Air pressure discharge furnace having protective atmosphere inlet and outlet

ABSTRACT

A furnace vessel for holding and pouring molten steel which vessel may be refilled intermittently while concurrently discharging molten steel at a controlled rate into a continuous casting mold. The furnace has a refractory lined and insulated reservoir which is pressurizable. Refractory lined and insulated pouring and filling spouts communicate with the bottom portion of the reservoir and extend vertically at least slightly above the maximum level of the steel in the reservoir. To prevent freezing of the metal in the spouts, heat generating means are provided at the top ends of the spouts and their bottom ends communicate with opposite ends of an inductively heated channel in the base of the reservoir. Also the cross sectional areas of the spouts are kept large with respect to their lengths so as to promote convection therein. The reservoir is pressurized to raise the liquid level above a flow restriction in the pouring spout and maintain the desired head above the bottom thereof to produce the required outflow rate. The flow restriction is designed to provide more precise control over the volumetric outflow rate of molten steel. Additional heat is supplied to the inlet and outlet ends of the flow restriction. Downstream from the flow restriction a means is provided for forming the cross sectional shape of the stream as it leaves the pouring spout. Protective atmosphere is provided for the exposed molten metal in the spouts.

United States Patent Allyn et al.

[ 51 May 14, 1974 AIR PRESSURE DISCHARGE FURNACE Inventors: Jerome B. Allyn, Graytown; John A.

MacDougall, Toledo, both of Ohio; John D. Nesbitt, Chicago, Ill.

266/40; 222/146 R, 146 HE, 146 H, 152, 394

[56] References Cited UNlTED STATES PATENTS 2,674,640 4/1954 Tama 222/394 2,552,648 5/1951 Poland 266/40 X 959,146 5/1910 MacCa11um.. 266/38 3,412,899 11/1968 Sutter 222/394 X 2,939,899 6/1960 EdStl'and et :11. 266/38 UX 3,221,379 12/1965 Shearman 222/394 X 2,568,525 9/1957 Waddington et a1. 222/152 X FOREIGN PATENTS OR APPLICATIONS Primary Examiner-Stanley H. Tollberg Assistant Examiner-David A. Scherber Attorney, Agent, or Firm-Henry Kozak [5 7] ABSTRACT A furnace vessel for holding and pouring molten steel which vessel may be refilled intermittently while concurrently discharging molten steel at a controlled rate into a continuous casting mold. The furnace has a refractory lined and insulated reservoir which is pressurizable. Refractory lined and insulated pouring and filling spouts communicate with the bottom portion of the reservoir and extend vertically at least slightly above the maximum level of the steel in the reservoir. To prevent freezing of the metal in the spouts, heat generating means are provided at the top ends of the spouts and their bottom ends communicate with opposite ends of an inductively heated channel in the base of the reservoir. Also the cross sectional areas of the spouts are kept large with respect to their lengths so as from the flow restriction a means is provided for forming the cross sectional shape of the stream as it leaves 1,138,187 10/1962 Germany 222/146 H the Ourin S out Protective atmos here is rovided P g P P P I for the ex osed molten metal in the s outs.

16 Claims, 7 Drawing Figures q 62 10 as J L 66 U \L 1 Iv .1 1

a I j 7o I'v "p 2 a .28 77 I 16 a I 1 1 l: x/ I t a; -L 24 22 1 I l 0 4 I 7a 80 78 1, a: 4 i 4 23 I S In 30 if? 9 l/ ha I 46 44 W AIR PRESSURE DISCHARGE FURNACE HAVING PROTECTIVE ATMOSPHERE INLET AND OUTLET This is a continuation, of application Ser. No. 60,452, filed Aug. 3, 1970, now abandoned.

BACKGROUND OF INVENTION This invention pertains to a furnace vessel for holding and pouring molten steel. More particularly, it relates to such a furnace vessel for supplying moltensteel at a controlled rate to a flow-through or continuous type chill mold device.

Although the concept of casting continuous strands of billet stock is very appealing the steel industry, this concept has not been universally accepted by the industry primarily because of the problems encountered in supplying a stream of molten steel to a casting mold at a controlled rate. Generally the prior art devices used for such purposes consisted of tiltable or bottom pouring ladles in combination with tundishes. Large tundishers were required if the contents of two or more ladles were to be consecutively poured without interruption. After an emergency shut-down or after each heat was poured, the tundishes usually required cleaning, including the removal of slag and solidified residual metal. Patching and partial replacement of the refractory lining were often required due to the chemical and physical erosion of the refractories, particularly the discharge orifices, and also due to the thermal and physical stresses incurred. Occasionally the mechanical I shut-off devices such as the tundish stopper rods failed to completely stop the outflow of molten metal because of erosion of its mating parts. Because of these problems, it was the practice to have a series of tundishes available with at least one of them being in a fully preheated and ready to used condition. Other difficulties included an inability to control flow rate within acceptable limits, formation of excessive slag,.clogging of the discharge orifices due to chilling or alumina build-up, inadequate control of metal temperature, and the fact that casting could not be started without having a ladle present to pour molten steel into the empty tundish.

Systems utilizing pneumatic pressure to cause molten metal to flow from a pressurized reservoir have been developed in recent years for pouring a number of successive casts or amounts, each having a volume less than the volume of the reservoir of the pouring vessel.

Examples of such devices are found in US. Pat. Nos. 3,465,916 of W. D. Hibbard et al. issued Sept. 9, 1969 and 3,412,899 of J. G. Sutter issued Nov. 26, 1968. However, even with the teachings of these patents and of other prior art, most of the above mentioned problems still prevailed with respect to the continuous casting of steel. In addition, other problems presented themselves when prior art pressure pouring systems were used for casting steel because they were designed primarily for lower melting point metals. One of the most serious problems was the frequent tendency of the molten steel to become chilled and solidified in the filling and pouring spouts due to the partial isolation of the metal in the spouts from the heat of the main body of molten steel in the reservoir.

SUMMARY OF lNVENTlON Generally speaking, the furnace vessel of this invention comprises a refractory lined interior reservoir having vertically disposed and refractory lined filling and pouring spouts communicating with respective openings in the bottom portion of the reservoir. Means are provided to pressurize the reservoir and raise the liquid level in the spouts until the required head is reached in the pouring spout to produce the desired flow rate out of the discharge orifice therein. The discharge orifice is designed and located so that the outflow can be made to vary'in proportion to about the first power or less of the height of the head above the orifice. This provides a means for more precise control of the outflow because a relatively large change in the head will produce a relatively small change in outflow. To prevent freezing of the molten steel in the orifice, even when the temperature of the outflowing steel is close to its temperature of fusion, additional heat is supplied adjacent both the inlet and outlet ends of the orifice. The pouring spout may be adapted for use with vertical or inclined chill molds. For inclined chill molds a snout member extends from the downstream end of the discharge orifice. This snout has a downwardly inclined trough with a replaceable lip member at the lower end of the trough. This lip member preferably is a horizontally disposed refractory plate which causes the cascading molten stream of steel to spread laterally just prior to its entrance into the casting mold.

Projecting beneath the bottom of the reservoir in a U shaped channel, the ends of which are beneath and closely adjacent the lower ends of the spouts. An inductive heating means is provided to heat the molten metal in the channel. The heat is conveyed by the molten steel in the channel to the surrounding steel in the bottom of the reservoir, and especially to the steel at the bottom of the spouts. Additional heat is supplied to the steel in the top portion of the spouts. Preferably the top of the filling spout has an annular burner which directs flames and products of combustion inwardly and downwardly. The flue gases from this burner contain as much as 40 percent combustibles so as to produce a non-oxidizing atmosphere to the iron in the steel. Electrical heating elements heat the top portion of the pouring spout which is supplied with a protective atmosphere such'as argon. The filling and pouring spouts are insulated'and their length to diameter ratios are kept small so as to enhance convection and reduce the possibility of freeze-up of the steel in the spouts.

It is a general object of this invention to produce a durable holding furnace. of the pressure pouring type for casting molten steel which maintains the steel in a molten state for prolonged indefinite periods even in the partially isolated filling and pouring spouts.

It is another object of this invention to produce a pressure pouring furnace vessel which is capable of receiving an incoming stream of molten steel from a ladle with a minimum of refractory erosion or damage.

It is another object of this invention to produce a pressure pouring furnace vessel having a pouring means which cases a stream of molten steel into the chill mold device to prevent a washing action thereon.

It is still another object of this invention to produce such a furnace vessel having a pouring spout with a flow restriction that enables the volumetric flow rate to be more precisely controlled.

It is yet another object of this invention to produce such a furnace vessel for molten steel wherein the steel in the reservoir and its filling and pouring spouts is atmospherically shielded from oxidation.

The above mentioned objects and other objects and advantages and the manner of attaining them will be apparent from the following detailed description of an embodiment of this invention made with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an elevational view of the pressure pouring type holding furnace vessel of this invention, shown in conjunction with a pass-through continuous strand casting apparatus at the pouring end thereof and a ladle positioned above the filling spout of the furnace vessel.

FIG. 2 is an enlarged cross sectional view of the furnace vessel in FIG. 1 taken along a vertical center plane paralleling the plane of the drawing of FIG. -1.

FIG. 3 is a sectional view taken along line 3--3 of FIG. 2 showing the offset in the filling spout.

FIG. 4 is a sectional view taken -along line 4-4 of FIG. 2 with parts broken away.

FIG. 5 is a lateral elevation view of the outer end of DESCRIPTION OF THE PREFERRED EMBODIMENT portion of the reservoir 18 that is exposed to direct contact with-the molten steel. The upper portion of the reservoir which is not in contact with the molten steel may be made of an air setting plastic refractory 26 which is less resistant to molten metal contact, but has sufficient structural strength and a high pyrometric cone equivalent, such as Mono 70. Since the molten metal should not contact the upper portion of the reservoir, this defines the maximum operating steel level.

Located centrally below the bottom of the reservoir 18- is an. inductive heating means 28 which embraces a vertically disposed U shaped tubular channel 30. The

Referring to the drawings, FIG. 1 shows the pressure -mold 12 where at least the outside of the strand be comes solidified. As the strand becomes solidified, it is continuously withdrawn from the mold, preferably ata constant speed'so as to promote product uniformity. The supply of molten steel in the furnace vessel is intermittently or continuously replenished from the ladle 14 at a relatively rapid rate' so that the ladle may be removed when empty and replaced by a full ladle while the molten steel is being continuously poured from the furnace vessel without interruption.

v The furnace vessel 10 has an exterior metal shell or casing 16 which houses a refractory lined reservoir chamber 18 and refractory lined filling and pouring spouts 20 and 22 respectively. These spouts 20 and 22 communicate with the bottom portion of the reservoir through openings 21 and 23, respectively, as best shown in FIG. 2. The shape of the reservoir is not critical and may be dictated by structural requirements, ease of fabrication, and thermal considerations. Round chambers which provide the lowest surface to volume ratios arepreferred. A suitable high temperature refractory 24 which is resistant to high temperature softening, such as Permanente 98, is used to line the lower channel ends open into a groove 32 extending across the bottom. of the reservoir so that the inductively heated metal may circulate upwardly into the main body of the reservoir, and particularly into the openings 21 and 23 of the filling and pouring spouts which are aligned vertically above the ends of the channel.

The flow of superheated metal caused by natural convection and the electromagnetic forces of the induction coil provides additional heat to the metal in the open-.

- ings 21. and 23. The minimum operating steel level at which the vessel is functional is the location where the openings 21 and 23 are just filled with molten metal. The filling spout 20 located on the left side of the reservoir in FIG. 2 receives the incoming molten steel from the ladle l4 and channels it into the reservoir 18. It may be made with the same refractory material that is used for the lower portion of reservoir 18. However, it was found that the turbulence caused by the stream of molten metal from the ladle as it entered the molten steel in the spout tended to rapidly erode the refractory, particularly if the spoutwere inclined.- To allevi-' ate the problem, the upper portion of the spoutcontaining the molten steel was made vertical for a length numerically equivalent to percent or more of the square root of the distance between the level of metal in the ladle and the level of metal in the pouring spout. The diameter of this vertical section is at least onequarter of its depth. With this arrangement the energy of the incoming ladle stream was dissipated harmlessly in the vertical portion of. the column of molten steel in the spout. The remaining or lower portion of the spout may be inclined towards its respective end of the inductor channel 30. Preferably, the upper portion of the filling spout and that portion of the lower portion of the spout underlying the column of steel in the upper portion are lined with a pre-fired sleeve 36 or pre-fired shapes (see FIGS. 3 and 4) made of an asphalt impregnated refractory, such as magnesium oxide, to reduce corrosion and erosion. The spout may be topped with a funnel shaped section 38 made from a coarse grained, high alumina castable refractory, such as Purotab Coarse. The length of the filling spout, as measured between its maximum and minimum steel levels is about 2-6 times its diameter or average lateral cross sectional dimension. To prevent fissures or cracks from extending through the relatively thin wall section between the spout and the reservoir, an artificial interface or barrier 40 is created by installing a sheet of dissimilar material, such as thin aluminum sheet, about midway between the spout and reservoir (see FIG. 2). This interrupts the monolithic character of the wall section so that a crack or fracture started on one side of the barrier will not propagate into the other side. It is important to prevent the formation of any artery in the refractory through which the pressurizing atmosphere can escape from the reservoir.

The inner refractory shape which forms the reservoir and spouts preferably is surrounded by layers of addi tional refractory. Generally each subsequent layer has lesser refractory properties and greater insulative properties. The layer 42 adjacent the inner refractory is a a i e y d nse 3..0.Q stotyi has a 2 3?: cent alumina, having greater structural strength and higher insulating qualities than the inner refractory. It also provides protection in case of a breakthrough in the inner refractory. The next outer layer of refractory may be 2 /2 inches of 2,800F. insulating firebrick 44 followed by 2% inches of 2,600F. insulating firebrick 46, and then a 3 inch layer of block insulation 48 which is refractory at l,900F. and has an insulative K factor of between about 0.5 and 0.8 The thicknesses and types of the refractory and insulating materials may be varied provided that the average K factor of the composite wall is about Btu-in./ft. -hr.-F. or less from the molten steel in the spout to exposed outer surfaces of the spouts and the ratio of the outside diameter of the spouts to their inside Eliai'neters is T or 'riiie. W

Associated with the top of the filling spout is a burner assembly -50 (see FIG. 2) which provides heat and an atmosphere which is non-oxidizing to the iron in the spout. The burner assembly-has a metal housing 52 lined with 1% inches of 3,000F. insulating firebrick '54 (see- FIG. 6). Inside the lining is a castable refractory, such as Greencast 97, which forms a vertically disposed cylindrical combustion chamber 56 and a superimposed coaxially aligned cylindrical opening 58 through which the steel may be poured while the burner is in operation. This opening 58 is about onehalf of the diameter of the combustion chamber 56 and provides a. means of escape for the partially restrained flue products from the combustion chamber. The fuel and air for the burner are mixed so as to provide a flue gas atmosphere containingabout 40 percent cornbust i: bles. Oxygen enriched or preheated air may be used. The fuel-air mixture is injected tangentially into the combustion chamber through a single tubular channel 60 to produce a circular flow or vortex. Hinges 61 are provided on one side of the burner assembly 50 so that it may be swung away from its normal position over the top of the filling spout when access to the filling spout is required for its inspection and repair.

The pouring spout 22 has approximately the same dimensions, length to diameter ratio, and insulation as the filling spout 20. However, since the velocity and turbulence of the molten steel flow is negligible in the pouring spout and there is no slag or FeO to contend with, there is no need of a protective pre-fired liner such as is required in the filling spout. The top portion of the spout is enclosed by a cover 62 so that the area above the molten steel may be flooded with a protective atmosphere, such as argon gas, supplied by an inlet pipe 64 to prevent the formation of slag on the exposed top of the molten steel. Resistance type electrical heating elements 66 are provided in the cover to supply additional heat to the top of the spout. The outer edge of the top of the spout has a lip section 68 which extends slightly above the maximum steel level in the reservoir.

A removable snout assembly 70 is attached to the lip section 68. This snout assembly contains a flow restriction 72, the volumetric outflow from which is proportional to about the first power or less of the height of the molten metal above the flow restriction. A round orifice flow restriction may be used, but it has the disadvantage of requiring a greater head-of molten steel to become submerged than is required to submerge a slot orifice having the same cross sectional size but less height. Preferably the flow restriction comprises a nozzle orifice that has a width to height ratio of between 1.5 :l and 3:1 so that it will be quickly submerged when the level of the steel in the pouring spout is raised to a pouring level. For a pouring rate of up to about 30 tons per hour produced by a head of 4 inches or less, a substantially rectangular nozzle opening having a width of 2 inches and a height of three-quarters of an inch was used to achieve a volumetric outflow that was proportional to the 7/ 10 power of the head. This provides a means for more precise control of the rate of outflow than could be obtained with a weir. The outflow from a non-submerged orifice or flow restriction varies to a greater extent per unit of head than that from a submerged orifice. Under circumstances wherein precise control of outflow rate is not as important, a broad crested weir or other type flow restriction may be used. Another advantage of this arrangement is that the washing effect of the outflowing molten steel stream on the refractory surfaces is minimized. Only low stream velocities are required to produce the desired volumetric outflow due to the large orifices which are used in conjunction with relatively low head pressures. Also with the large orifices there is less likelihood of the metal freezing in them.

The stream of molten steel issuing from the orifice flows down a trough 74 which is inclined at an angle of between 1 and 20 to the horizontal. At the lower end of the trough the angle flattens into a horizontal section 76. The width of the trough is from 1 to 6 times the width of the nozzle orifice. Electrical heating elements 77 of the resistance type are imbedded in the refractory ceiling above the trough to supply heat to the downstream end of the flow restriction 72. An expendable refractory tip 78 is located a short distance below and extends at least 2 inches beyond the end of the horizontal section 76. This easily replaceable tip 78 comprises a horizontally disposed refractory plate 80 with two vertically disposed side walls 82 and 84, preferably made of alumina splits. The purpose of this tip is to spread the stream of molten steel across substantially the entire width of the pool of steel in the mouth of the chill mold. This is accomplished by the direction change of the metal as it leaves the edge of step 76 and falls on tip 80. The centrifugal forces involved result in a flattening and spreading effect, which forces the metal to flow outward to the side limits 82 and 84 of the tip. A uniformly dispersed, thin stream of metal results, even if the stream leaving the step 76 is concentrated and non-uniform. The stream dimensions and character are repeatable with each new tip, thus removing the problem of a gradually varying stream character due to refractory erosion of the trough. This is particularly advantageous when pouring into a continuous belt type chill mold as shown in FIG. 1 because a narrow concentrated stream would wash the lubricant coating from the belt and melt through the belt. Preferably, the stream is dispersedlaterally so that the flow rate per hour is not greater than about 5 tons per inch of belt width. Thus, for a 30 ton per hour casting rate the stream is spread substantially uniformly across about 6 or 7 inches of belt width. It may be spread across almost the entire usable width of the belt or chill mold. The side walls 82 and 84 are used tolimit the width of the stream according to requirements. The relatively low height of the tip 78 allows it to be inserted deeply into the open end of the inclined chill mold 12 so that the stream of molten steel will fall centrally into the pool of molten steel in the mold rather than at the pool edge or directly onto the belt of the chill mold, thereby reducing the local heat transfer to the belt. The dimensions given may be scaled upwards or downwards in proportion to each other in accordance with'the pouring rate desired. Argon or the like inert atmosphere is supplied to the enclosed space above the trough through an inlet pipe 86 to prevent slag formation on the steel. It is supplied at a rate that is sufficient to cause enough of an outflow from the end of the snout to protectively blanket the pool of steel in the chill mold. I

The snout assembly 90 shown in FIG. 7 is similar to the reservoir. Provision may also be made for the introduction of alloy ingredients to the reservoir through a pressurizable inlet chamber 114 incorporated with 'the atmosphere inlet manifold. The slag which forms on the molten steel in the filling spout may be removed or treated from time to time to maintain its desired consisthe snout assembly 70, but is adapted for discharging molten steel into a vertically disposed mold rather than an inclined mold. It comprises a refractory chamber into which molten steel flows from the pouringspout when the levelof the steel in the spout is raised to a pouring level. Molten steel is discharged through a vertically disposed nozzle 92 located in the floor 94 of the chamber. The floor is inclined slightly so that the mo]- ten steel in the chamber which is not discharged through the nozzle returns to the spout when pouring is terminated. Heating means 96 and 98 are provided respectively in the ceiling of the chamber adjacent the inlet end of the nozzle and in the shroud 99 which depends from around the outlet end of the nozzle. Argon or the like inert atmosphere is supplied through lines 100 and 102 respectively to the space above the molten steel in the pouring spout and around the nozzle outlet.

To begin theoperation of the furnace vessel 10, the preheated reservoir is purged with argon or the like inert atmosphere which is supplied under pressure through the top of the reservoir via main atmosphere inlet pipe 104. Then molten steel is poured from the ladle into the filling spout 20 of the furnacevessel at least up to the minimum operating level. At any time thereafter, pouring from the vessel 10 may be initiated by increasing the atmospheric pressure in the reservoir. Thereafter the rate of outflow is controlled by a regulator 106 which is responsive to a signal from a detector 108 which senses the level of the molten steel in the pouring spout 22. When the liquid level is too low in the pouring spout, the regulator responds by increasing the atmospheric pressure in the reservoir. Conversely, when the liguid level is too high, the regulator reduces the pressure, such as by opening vent means 1 10 communicating with the reservoir. The caster pool level may be controlled also by varying the speed with which the partially chilled strand of steel is withdrawn from the chill mold. However, for the sake of product uniformity, it is preferred that the strand be withdrawn from the chill mold at a substantially constant speed.

A radiation pyrometer 112 may be provided to determine the temperature of the molten steel in the reservoir. Preferably the lens of the pyrometer is located in the atmosphere inlet manifold so that the lens is swept by the incoming gas stream and thereby protected from dust and hot corrosive gases which may be present in tency and chemical composition. A tilting means 116 is provided to rotate the furnace vesselso that its entire contents may be emptied through the filling spout 20. Normally the vessel is emptied only when repairs are required on the refractory of the reservoir. Repairs to the refractory lining of the filling spout may be made without emptying the reservoir..

While the above description was made with reference to the presently preferred embodiment shown in the accompanying drawings, it is to be understood that the scope of the invention is not necessarily limited to the details shown in these drawings, but rather is limited only by the attached claims.

We claim:

1. A furnace vessel for holding and continuously supplying molten steel to a casting mold, comprising: a pressurizable vessel having a chamber therein, generally vertically inclined filling and pouring spouts received within said vessel, the upper portions of said spouts being located above the ceiling of said chamber, generally horizontalopenings providing communication between said filling and pouring spouts and the bottom portion of said chamber, means for supplying a gas under pressure to said chamber, means for supplying heat to at least a portion of said chamber, combustion means for supplying heat and protective atmosphere to the top portion of said filling spout, and means for supplying heat and protective atmosphere to the top of said pouring spout.

2. A furnace vessel according to claim 1 wherein the ratio of the diameter of the spouts to the length equivalent to the distance between the upper portion of said chamber and the horizontally extending openings is between about 1:2 and l:6.

3. A furnace vessel according to claim 1 wherein said filling and pouring spouts are both insulated on the out sides thereof so that the K factor of the composite refractory and insulative wall of each spout as measured betweenthe inner and outer walls of the spout is 10 4. A furnace vessel according to claim 1 wherein said pouring spout includes a discharge flow restriction which is designed to provide an outflow rate that varies proportionately to the 7/10 power or a greater power of the height of the molten steel thereabove.

5. A furnace vessel according to claim 1 wherein said pouring spout includes a discharge flow restriction having means for supplying heat adjacent its entrance and outlet ends.

6. A furnace vessel according to claim 5 wherein said flow restriction is an inclined orifice member with an inlet opening having a width to height ratio of between l.5:l and 3:1 so that it will be completely submerged by the head of molten steel required to produce the desired outflow rate.

7. A furnace vessel according to claim 1 wherein said vessel is adapted for discharging into an inclined mold and said pouring spout is provided with an inclined discharge chute having a horizontally disposed planar shelf at the lower end thereof, whereby a concentrated stream of molten steel flowingdown the chute will be caused to be flattened and spread laterally.

8. A furnace vessel according to claim 7 wherein said shelf is removably attached to the lower end of said chute and has vertically extending side walls to limit the width of the stream.

9. A furnace vessel according to claim 1 wherein said combustion means comprises refractory wall means defining a combustion chamber section and flue section which jointly extends therethrough and are coaxially aligned with each other and with the top section of said filling spout whereby an incoming stream of molten steel from a refilling ladle may be poured through said combustion means while it is in operation.

10. A furnace vessel according to claim 9 wherein said combustion means includes a fuel rich burner means capable of supplying an atmosphere containing about 40 percent combustibles to the top of filling spout and around said incoming stream.

11. A furnace vessel for holding and supplying molten steel to a casting mold, comprising: a pressurizable vessel having a central chamber therein; generally vertically inclined filling and pouring spouts communicating with the bottom portion of said chamber and extending upwardly therefrom to above the ceiling of said chamber, said spouts having a diameter to length ratio of between about l:2 and 1:6, said length being measured from where the spouts communicate with said chamber to said ceiling; means for supplying heat to the metal in said chamber and spouts; combustion means for supplying heat and protective atmosphere to the top portion of said filling spout; means for supplying a gas under pressure to said chamber; means for restricting the discharge flow associated with said pouring spout to control the outflow of steel therefrom; and means for supplying heat and protective atmosphere to the top portion of said pouring spout and to the inlet and outlet ends of said flow restriction.

12. A furnace vessel according to claim 11 wherein v 13. A furnace vessel according to claim 11 wherein said vessel is adapted for discharging into an inclined mold and said pouring spout is provided with an in clined discharge chute having a horizontally disposed planar shelf at the lower end thereof, whereby a con-' centrated stream of molten steel flowing down the chute will be caused to be flattened and spread laterally.

14. A furnace vessel according to claim 11 wherein said pouring spout includes a discharge flow restriction which is designed to provide an outflow rate that varies proportionately to the 7/10 power or a greater power of the height of the molten steel thereabove.

15. A furnace vessel according to claim 11 wherein said filling and pouring spouts are both insulated on the outsides thereof so that the K factor of the composite refractory and insulative wall of each spout as measured between the inner and outer walls of the spout is 10 Btu-in./ft. -hr.-F. or less.

16. A furnace vessel for receiving moltensteel from a ladleand holding and continuously supplying the molten steel to a casting mold, comprising: a pressurizable housing having a chamber therein; a pouring spout extending from the top of the housing to the chamber and having an inclined flow restriction at the end removed from the chamber; a filling spout extending from the top of the housing with its upper portion vertically disposed and its lower portion extending at an angle to communicate with the lower portion of said chamber, the location at which said filling spout is directed at an angle being located between the top of said chamber and the point at which said lower portion communicates with said chamber; the vertical distance between said location and the pouring spout flow restriction having a length numerically equivalent to at least percent of the square root of the vertical distance from the top of the ladle to said pouring spout flow restriction; means for supplying a gas under pressure to said chamber; means for supplying heat to at least a portion of said chamber; combustion means for supplying heat and protective atmosphere to the top portion of said filling spout; and means for supplying heat and protective atmosphere to the top of said pouring spout. 

1. A furnace vessel for holding and continuously supplying molten steel to a casting mold, comprising: A pressurizable vessel having a chamber therein, generally vertically inclined filling and pouring spouts received within said vessel, the upper portions of said spouts being located above the ceiling of said chamber, generally horizontal openings providing communication between said filling and pouring spouts and the bottom portion of said chamber, means for supplying a gas under pressure to said chamber, means for supplying heat to at least a portion of said chamber, combustion means for supplying heat and protective atmosphere to the top portion of said filling spout, and means for supplying heat and protective atmosphere to the top of said pouring spout.
 2. A furnace vessel according to claim 1 wherein the ratio of the diameter of the spouts to the length equivalent to the distance between the upper portion of said chamber and the horizontally extending openings is between about 1:2 and 1:6.
 3. A furnace vessel according to claim 1 wherein said filling and pouring spouts are both insulated on the outsides thereof so that the K factor of the composite refractory and insulative wall of each spout as measured between the inner and outer walls of the spout is 10 Btu-in./ft.2-hr.-*F. or less.
 4. A furnace vessel according to claim 1 wherein said pouring spout includes a discharge flow restriction which is designed to provide an outflow rate that varies proportionately to the 7/10 power or a greater power of the height of the molten steel thereabove.
 5. A furnace vessel according to claim 1 wherein said pouring spout includes a discharge flow restriction having means for supplying heat adjacent its entrance and outlet ends.
 6. A furnace vessel according to claim 5 wherein said flow restriction is an inclined orifice member with an inlet opening having a width to height ratio of between 1.5:1 and 3:1 so that it will be completely submerged by the head of molten steel required to produce the desired outflow rate.
 7. A furnace vessel according to claim 1 wherein said vessel is adapted for discharging into an inclined mold and said pouring spout is provided with an inclined discharge chute having a horizontally disposed planar shelf at the lower end thereof, whereby a concentrated stream of molten steel flowing down the chute will be caused to be flattened and spread laterally.
 8. A furnace vessel according to claim 7 wherein said shelf is removably attached to the lower end of said chute and has vertically extending side walls to limit the width of the stream.
 9. A furnace vessel according to claim 1 wherein said combustion means comprises refractory wall means defining a combustion chamber section and flue section which jointly extends therethrough and are coaxially aligned with each other and with the top section of said filling spout whereby an incoming stream of molten steel from a refilling ladle may be poured through said combustion means while it is in operation.
 10. A furnace vessel according to claim 9 wherein said combustion means includes a fuel rich burner means capable of supplying an atmosphere containing about 40 percent combustibles to the top of filling spout and around said incoming stream.
 11. A furnace vessel for holding and supplying molten steel to a casting mold, comprising: a pressurizable vessel having a central chamber therein; generally vertically inclined filling and pouring spouts communicating with the bottom portion of said chamber and extending upwardly therefrom to above the ceiling of said chamber, said spouts having a diameter to length ratio of between about 1:2 and 1:6, said length being measured from where the spouts communicate with said chamber to said ceiling; means for supplying heat to the metal in said chamber and spouts; combustion means for supplying heat and protective atmosphere to the top portion of said filling spout; means for supplying a gas under pressure to said chamber; means for restricting the discharge flow associated with said pouring spout to control the outflow of steel therefrom; and means for supplying heat and protective atmosphere to the top portion of said pouring spout and to the inlet and outlet ends of said flow restriction.
 12. A furnace vessel according to claim 11 wherein said combustion means comprises refractory wall means defining a combustion chamber section and flue section which jointly extend therethrough and are coaxially aligned with each other and with the top section of said filling spout whereby an incoming stream of molten steel from a refilling ladle may be poured through said combustion means while it is in operation.
 13. A furnace vessel according to claim 11 wherein said vessel is adapted for discharging into an inclined mold and said pouring spout is provided with an inclined discharge chute having a horizontally disposed planar shelf at the lower end thereof, whereby a concentrated stream of molten steel flowing down the chute will be caused to be flattened and spread laterally.
 14. A furnace vessel according to claim 11 wherein said pouring spout includes a discharge flow restriction which is designed to provide an outflow rate that varies proportionately to the 7/10 power or a greater power of the height of the molten steel thereabove.
 15. A furnace vessel according to claim 11 wherein said filling and pouring spouts are both insulated on the outsides thereof so that the K factor of the composite refractory and insulative wall of each spout as measured between the inner and outer walls of the spout is 10 Btu-in./ft.2-hr.-*F. or less.
 16. A furnace vessel for receiving molten steel from a ladle and holding and continuously supplying the molten steel to a casting mold, comprising: a pressurizable housing having a chamber therein; a pouring spout extending from the top of the housing to the chamber and having an inclined flow restriction at the end removed from the chamber; a filling spout extending from the top of the housing with its upper portion vertically disposed and its lower portion extending at an angle to communicate with the lower portion of said chamber, the location at which said filling spout is directed at an angle being located between the top of said chamber and the point at which said lower portion communicates with said chamber; the vertical distance between said location and the pouring spout flow restriction having a length numerically equivalent to at least 75 percent of the square root of the vertical distance from the top of the ladle to said pouring spout flow restriction; means for supplying a gas under pressure to said chamber; means for supplying heat to at least a portion of said chamber; combustion means for supplying heat and protective atmosphere to the top portion of said filling spout; and means for supplying heat and protective atmosphere to the top of said pouring spout. 